The present invention relates generally to a hydraulic valve lifter for a variable displacement engine of an automobile.
When an automobile having a multi-cylinder engine is running under low load conditions at relatively constant speed, descending a long hill, decelerating or idling, it is unnecessary to operate all of the cylinders of the engine. In order to save fuel consumption and to improve gas mileage, there have been proposed various types of hydraulic valve lifters to effectively perform a variable displacement of the multicylinder engine.
One such prior art lifter includes a body member, a plunger member slidably disposed within the body member and operatively connected to one end of a rocker arm; a pressure chamber defined by the body member and the plunger member, and a reservoir chamber formed in the plunger member and connected to the pressure chamber through a check valve. When the corresponding engine cylinders are not in use due to one of the above conditions of automobile operation, the check valve will be maintained at the open position by a solenoid valve thereby allowing a fluid flow from the pressure chamber to the reservoir chamber. Accordingly, the fluid in the pressure chamber will not generate a pressure increase and the rigidity of the lifter will be removed.
Such prior art, however, discloses also that the diameters of the plunger member and the body member bore are substantially the same, i.e., the outer diameter of the plunger member being substantially equal to the inner diameters of the body member. According to such a structure, since the amount of hydraulic fluid flow is considerably large, the slidable movement of the plunger member may not be effectively carried out. On the other hand, if the inner diameter of the body member is lessened in order to avoid the problems, the size of the check valve therein should be reduced accordingly, which will not meet the required functions of the check valve.